Instrument caging mechanism



L. D. CAHILL ET AL INSTRUMENT CAGING MECHANISM 2 Sheets-Sheet 1 Filed Dec. 5, 1945 INVENTORS LYSLE D. CAHILL WALTER T. BUHL BY ALFRED S.

HORWITZ ATTORNEY 1949' 1.. D. CAHILL ET AL INSTRUMENT CAGING MECHANISM Filed Dec. 5, 1945 2 Sheets-Sheet 2 AIIIIII 1?) VIII INVENTORS LYSLE D. CAHILL WALTER T. BUHL Y ALFRED S. HORWITZ ATTORNEY Patented Jan. 18, 1949 INSTRUMENT QAGING MECHANISM -.Lysle D.- Cahill, 'south -Euclid; and =Walter 'I. -Buh1 S. lHorwitz, Shaker Heights, ()hio,

*assignors, by mesne assignments, to Jack & 3 Heintz irecision Jndustries, Inc Cleveland,

.Ohio, a corporation. of Delaware Application December 5, 1945,Serial No.'6-32;934

Claims This invention relates to caging mechanisms tor: aircraft automatic .pilot instruments and has for .a primary object to provide an automatic mechanism for caging and uncaging an instrument. p p l A more particular object is to provide a caging mechanism for an aircraft automatic pilot instrument which automatically uncages the instrument when the automatic pilot is engaged and cages the instrument when the automatic pilot is disengaged.

Another object is to provide a caging mecha nism for an aircraft automatic pilot which cooperates. with a cardioid cam on agyro gimbal for moving the gimbaltoits caged position and locking it there.

(A furtherbbject is to provide a caging mechanism for an aircraft automatic pilot whichauto: matically cages the automatic pilot in response to a failure in the automatic pilot hydraulic system. .Vtfiththe foregoing and other objects in View the invention .resides in the followingspecification and appended claims, certainembodiments and details of construction of which are shown in the accompanying drawings, in which:

Figure 1 is a partially cutaway View of a tilted automatic pilot instrument employing two of the caging mechanisms;

Figure 2 is an enlarged sectional view in elevationof the caging mechanism in the uncaged position;

Figure 3 is .an enlarged sectional view in elevation of the caging mechanism in the caged or locked position.

Referring moreparticularly to -Figures 2 and 3 a substantially U-shaped'mounting frame I is shown fixedly supporting a cylinder 2 by means of a threaded section 3. Carriedwith the cylinder is a piston 4 having a seal 5. Secured to piston 4 by means of two lock nuts 6 and 1 is a piston rod 8, which extends through both legs 9 and IU of the U-shaped mounting frame I. A sleeve II is provided in leg H) as a guide for piston rod 8. A seal I2 is inserted between sleeve H and piston rod 8 for preventing pressure fluid leaks from within the cylinder 2.

Keyed to the piston rod 8 by a key I3 is a collar M. A compression spring l5 surrounds the piston rod 8 and engages the collar l4 at one end and the sleeve l I at the other end. The spring normally holds the piston rod 8 in the position shown in Figure 3 with the piston 4 in its retracted position. A fluid passage [6 leading to cylinder 2 is provided in frame I. On

a i ,2 the Lendofmod 8 is an engaging ball l -T which, when the rod is extended, engages-a detent H8 in acardiold cam lit-obtaining a locking relationship, as in Figure 3. Cihetcam iii isshown fixedly attached to -a fragmentaryportion of 1a gimbatiil in .a gyro assemblyat the pivot -2 l of thegimbal .InFigure 1 twoidentical caging mechanisms 22 and 23, details of whichare similar .to the one ..previously described and shown in Figures and 3, are installed within an'hydraulictautomatic pilot box 24. Agyro. assembly .shown in the automatic pilot box it consists essentially of an outer frameiZS, a-gin'ibaltzilpivnted axially within theirame 25,..aninner. gimbal. 21 .pivoted within girrib'alZQ with a pivot axis at right angles to the axis of gimbal 2i] and a rotor Zlltpivoted within the inner gimbal Z'iandhaving itsaxis at right anglesto thegimbal axis. A bail .arm 29 "having a bearing member 38 is secured to inner gimbal 2'! by a pin 3!.

An upper bearing housing 32 and a lower bearing housing '33 'pivotally support a bail 1track.assembly 34 which is internally slidably engaged v by bearing member 38 of the bail arm 29. Fixed to the end of bail track assembly 34,.atljacent to the lower bearing housing '33, is a cardioid cam 35 which is shown in dotted'lines'in"the figure. A second cardioid cam "i9 is shown "in dotted lines mounted on gimbal 20 at its,pivot point 2 I. Also locatedat pivot point 2 l in frame 25 isapick-off assemblyflswhich is nota part ofthe invention.

*Caging mechanism 22 is positioned on the "base for engagement and *disengagement with cam 35, therebylocking or freeingtheinner gimbal 21 through bail arm 1 28 and bail track 34- during caging and unoaging-operations.

'Caging -mechanism -23 is positioned on the frame 25 for engagement and disengagement with cam l9, thereby locking or freeing the gimbal 20, during caging and uncaging operations.

Operation of the caging mechanism is best understood by referring to Figures 2 and 3. As the automatic pilot is turned on, fiuid pressure is transmitted through fluid passage l6 into cylinder 2. The force exerted by the pressure fluid on piston 4 overcomes the force exerted by spring l5 and the piston rod is moved away from engagement with detent H! in cam 19. Gimbal 20 is then free to move about pivot 2|.

When the automatic pilot is turned off, no fluid pressure is transmitted to cylinder 2, therefore the force exerted by spring l5 retracts piston 4 and extends piston rod 8 until engaging ball ll engages cam l9 and eventually detent I8 in cam l9. Detent I8 is located at the point of smallest radius on cam I9. Since the principle of a cardioid cam is that the cam rider, in this case the piston rod 8, is always at the same angle with a tangent at the point of rider contact on the cam, no matter what position the gimbal 20 is in at the time cam I9 is engaged, the cam will cooperate with the force of spring H) to move the gimbal until ball I! engages detent 18 in a locking relationship.

4 Thus it is seen that a positive automatic caging mechanism is provided for use with gyroscopic assemblies, essentially hydraulic automatic pilots, wherein during operation of the assembly or pilot the gimbals are uncaged and upon cessation of operation of the assembly or pilot the gimbals are caged.

We claim:

1. A caging mechanism for use with gyroscopic assemblies having a gimbal frame, comprising a substantially U-shaped mounting frame, a cylinder secured to one side of said U-shaped frame, a piston within said cylinder, a piston rod slidably extending from said piston and from said cylinder through both legs of the U-shaped frame, a sleeve fixedly secured to said U-shaped frame for guiding the piston rod, a collar on the piston rod, positioned between the legs of the U- shaped frame, a spring held under compression between the collar and the sleeve for said piston rod in locked position with said gimbal frame to cage the same, and a passage in the frame for leading pressure fluid into the cylinder to overcome said spring and uncage the gyro.

2. A caging mechanism for use with gyroscopic assemblies having a gimbal frame, comprising a mounting means for said caging mechanism, a cylinder carried by the mounting means, a piston located within said cylinder, a piston rod fixed to said piston and associated with said mounting means, resilient means for holding the piston rod in the extended position to engage said gimbal and cage said gyro and a passage in said mounting means for leading pressure fluid into said cylinder for overcoming the holding action of said resilient means for moving the piston rod to its retracted position out of engagement with said gimbal to uncage the gyro.

3. A caging mechanism for use in gyroscopic assemblies having a gimbal, comprising mounting means for the caging mechanism in the gyroscopic assembly, a cylinder carried by said mounting means, a piston located within said cyl- 55 inder, a piston rod fixed to said piston and associated with said mounting means, resilient means for normally holding the piston rod in the extended position, means fixed to said gimbal for 4 receiving said extended piston rod and for caging said gimbal, and a passage in said mounting means for leading pressure fluid into said cylinder for overpowering said resilient means and retracting the piston rod from its engagement with the gimbal means leaving the gimbal uncaged.

4. A caging mechanism for use in gyroscopic assemblies with a gimbal, comprising mounting means for the caging mechanism in the gyroscopic assembly, a cylinder carried by said mounting means, a piston located within said cylinder, a piston rod fixed to said piston and associated with said mounting means, resilient means for normally holding the piston rod in the extended position, a cam fixed to said gimbal in alignment with the piston rod, a. detent in said cam, means responsive to the resilient extending means of the piston cooperating with the eccentricity of the cam for moving the gimbal until the piston rod engages the detent, and a passage in said mounting means for leading pressure fluid into said cylinder for overpowering said resilient means and retracting the piston rod from its engagement with the detent leaving the gimbal uncaged.

5. A caging mechanism for use in gyroscopic assemblies having a gimbal, comprising mounting means for the caging mechanism in' the gyroscopic assembly, a cylindercarried by said mounting means, a piston located within said cylinder, a piston rod fixed to said piston and associated with said mounting means, resilient means for normally holding the piston rod in the extended position, a cardioid cam fixed'to said gimbal in alignment with said piston rod, adetent at the point of smallest radius on the cardioid cam for receiving the extended piston rod and thereby locking the gimbal in a caged position, and a passage in said mounting means for leading pressure fluid into said cylinder for overpowering said resilient means and retracting the piston rod from its engagement with the cardioid cam leaving the gimbal uncaged.

LYSLE D. CAHILL. WALTER T. BUHL. ALFRED S. HORWITZ.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,207,850 Brandt July 16, 1940 2,207,875 Roland July 16, 1940 2,273,309 Zand Feb. 17, 1942 2,393,124

Smith Jan. 15, 1946 

